Messages in this thread | | | Date | Sat, 9 Oct 2021 12:00:37 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH] static_call: fix null-ptr-deref in static_call_del_module |
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On Sat, Oct 09, 2021 at 03:44:28PM +0800, Wang Hai wrote: > I got a NULL pointer dereference report when doing fault injection test: > > BUG: kernel NULL pointer dereference, address: 0000000000000009 > ... > RIP: 0010:static_call_del_module+0x7a/0x100 > ... > Call Trace: > static_call_module_notify+0x1e1/0x200 > notifier_call_chain_robust+0x6f/0xe0 > blocking_notifier_call_chain_robust+0x4e/0x70 > load_module+0x21f7/0x2b60 > __do_sys_finit_module+0xb0/0xf0 > ? __do_sys_finit_module+0xb0/0xf0 > __x64_sys_finit_module+0x1a/0x20 > do_syscall_64+0x34/0xb0 > entry_SYSCALL_64_after_hwframe+0x44/0xae > > When loading a module, if it fails to allocate memory for static > calls, it will delete the non-existent mods (mods == 1) in the > static_call_module_notify()'s error path. > > static_call_module_notify > static_call_add_module > __static_call_init > site_mod = kzalloc() // fault injection > static_call_del_module // access non-existent mods > > This patch fixes the bug by skipping the operation when the key > has no mods. > > Fixes: a945c8345ec0 ("static_call: Allow early init") > Signed-off-by: Wang Hai <wanghai38@huawei.com> > --- > kernel/static_call.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/static_call.c b/kernel/static_call.c > index 43ba0b1e0edb..c3f8ffc5a52f 100644 > --- a/kernel/static_call.c > +++ b/kernel/static_call.c > @@ -400,7 +400,7 @@ static void static_call_del_module(struct module *mod) > > for (site = start; site < stop; site++) { > key = static_call_key(site); > - if (key == prev_key) > + if (key == prev_key || !static_call_key_has_mods(key)) > continue; > > prev_key = key;
Should you not update prev_key in that case? Also have you looked at jump_label_del_module() which is very similar in construction?
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